20 seconds is the minimum time you should wash your hands.
By the way, October 15th is Global Handwashing Day. With proper handwashing, respiratory and intestinal diseases can be reduced by 25–50%.
Source: https://www.cdc.gov/handwashing/when-how-handwashing.html
Photo: https://www.pexels.com/de-de/foto/hande-frau-wasser-zimmer-4031819/